This invention relates to panel assemblies, and particularly to flush-mounted panel assemblies having a gasket mounted on a single side and used as panels or windows in vehicles, buildings or other structures, as well as a method and apparatus for making such panel assemblies.
Relatively recent in the history of vehicle window panel assemblies, gaskets have been molded or extruded directly on to the window panel. In molded window panels, a sheet of glass is closed within a molding tool, and a polymeric material is then injected around the peripheral edge on the opposing surfaces, thereby capturing the peripheral edge of the glass panel within the injected polymeric material. After the material has cured, the mold is opened and the panel assembly is removed. To retain the modular panel assembly within the vehicle, studs or clips may be molded within or attached to the gasket and panel and used to engage the pinch flange forming the vehicle opening. Alternatively, or in addition thereto, a bead of adhesive can be applied to bond the panel assembly directly to the pinch flange.
New styling requirements are calling for flush-mounted glass panels having an exposed peripheral edge on the glass panel. One flush-mounted vehicle panel assembly on the market includes an extruded gasket of a thermosetting material deposited directly on one surface of a glass sheet. Often the extrusion includes two adhesive beads of polyurethane compounds, one deposited by the panel assembly manufacturer and the other applied by the vehicle assembler. Disadvantages associated with the extruded gaskets include long cure time for the first bead, adding cycle time to manufacturing. In addition, the gasket material used in forming the extruded gasket is typically not UV stable by itself and can degrade over time. Moreover, the extrusion does not easily adapt itself to receive mounting studs or clips. In addition, gaskets having a variable cross section cannot easily be formed using the extrusion method. Moreover, the extrusion compound is expensive and requires special storage and handling once formed.
Another window assembly intended for use in flush-mounted applications is a gasket of a thermosetting material molded directly to a single surface of a panel in a molding machine using reaction injection molded (RIM) urethane. Although this technique offers some variable cross sections, disadvantages include instability when subjected to prolonged exposures of UV light, a long cycle time in forming, and increased material costs compared with other materials such as thermoplastic elastomers, and in particular, thermoplastic vinyls including PVC. In addition, tensional or shear force applied between the glass and the gasket results in failure of the adhesive seal of the gasket with the panel as opposed to the desired loss of cohesion in the gasket itself.
None of the prior panel assemblies or methods provide flush-mounted gaskets having adhesion and bonding characteristics where the cohesiveness of the gasket fails under shear and peel tests after prolonged soaking in water. In particular, the prior methods or panel assemblies fail to provide a flush-mounted gasket having adhesion and bonding characteristics between gasket and panel surface which withstand a shear force in excess of 300 pounds per square inch or a 180 degree peel test greater than 30 pounds per linear inch after being soaked in 80.degree. C. water for 250 hours or more. Any resulting failure occurs in the adhesion of the gasket to the panel surface.
Thus, a need has existed in the industry for an excellent, reliable, high strength bond formed between the panel surface and the gasket of a flush mounted panel assembly having a single-sided gasket wherein the bond is capable of withstanding prolonged exposure to water. Such bond should not degrade or erode because of water wicking between the panel surface and the gasket, which in prior assemblies results in the failure of the gasket to panel bond in tests.